'97 S10 4.3 Liter - Got spark, got fuel, turns over - won't start!
 

I just purchased a '97 S10 Blazer with a 4.3 liter Vortec TBI V6/auto trans. The rig is in great shape and I got it for a great price. The person I bought it from says that his mechanic says it needs a new engine. I asked him what happened and he said that it over-heated and just wouldn't ever start again. His mechanic told him that it needed a new motor because the overheating caused the rings to lose their seat and that there's no compression. The only way to fix it would be to replace or re-build. I'm sure most of you on here can smell what I'm smelling about his diagnosis.

When I got home today after towing it 60 miles, I opened the hood to see what was going on. Well, first of all, there wouldn't be any compression because the spark plugs were finger-tight in their sockets. Second, the plug wires were unplugged and hanging there. Third, the fuse to the engine computer was pulled out and sitting in the ashtray. I feel bad for the guy I bought it from, but I really needed this vehicle.

The problem: After putting everything back together and in proper order, I attempted to start the motor. It turns over just fine, but won't start. I checked for spark at #1 and it looked good, though the plug was not the chocolate brown I like to see - it was pretty toasty looking. There is fuel in the line and appears to be plenty of pressure. I get fuel when I check the Schrader valve, and got squirted in the face with gasoline when I pulled the lines next to the throttle body. The battery is brand new, the fuses are all intact, and the starter is smooth and quiet. I tried starter fluid and even dumped about a quarter cup of fuel into the throat and still - no start.

I'm at a complete loss and need advice and guidance, please. I've heard of vehicles over-heating and then not starting until whatever sensor that caused it to shut off is cooled completely. As for which sensor? I'm at a loss. I'll start with the cheap, quick, and easy by replacing the spark plugs, but as I said before, there's a good, hot spark - at least at #1. Not enough fuel pressure? If that were the case, it would start of I primed it and die when it burned out the primer fuel. Fuel pressure regulator? Throttle position sensor? Something else entirely? I'm scratching my head at this one.

Any help, advice, or even ideas would be very appreciated. I'm a Scout Master and need to get this running by this weekend (10-12) to transport scouts to a weekend camping trip. Thank you so much in advance.

The best way to tell if have you have decent compression is to have a cylinder leak test done. A leak test is done with the piston at Top Dead Center with both the intake and exhaust vavles closed, then a metered amout of compressed air in force into the cylinder through the spark plug hole. If a cylinder is not holding air, it's leaking out from somewhere. A leaking head gasket will cause air to leak into cooling system, leaking valves will leak into either the intake or exhaust or both (if it's bad), and if the rings and cylinder are worn the air escape through the engine oil filler cap (or oil dipstick). A cylinder leak tester requires a constant supply of compressed air work, so you may have to take the truck a trusted repair shop to the have it tested.

Also, make sure your spark timing is good and not completely out of order. If the guy who was working on the vehicle didn't do the timing right; you could have cylinder no. 1 fire, when no. 4 should be firing. The firing order on a 4.3L is 1-6-5-4-3-2. The HEI ignition uses a traditional sytle distributor cap, while the EDI ignition uses a flat cap usualy what cylinders are suppose to be connected printed in small numbers on the cap.

Check fuel pressure and leakdown first. It's quick, easy and cheap, and it tells you the overall condition of the fuel delivery system. Most auto parts stores rent & sell fuel pressure testers. If you're planning on keeping this vehicle for a while, consider spending the $40 to put a necessary tool in your tool box. You'll use it more than you think ;)

Ignition ON, engine OFF, fuel pump running: Pressure must be 60psi to 66psi and must remain above 55psi for at least 10 minutes after the pump shuts off. If it fails any part of this test, further diagnosis is necessary to pinpoint the problem in the fuel delivery system.

1997 has a known issue with the ignition switch that can easily cause symptoms like you describe, (has fuel and spark and no-start).

Thanks everyone for the responses and advice. I decided yesterday to just bypass all of the tests and tear into this motor's fuel delivery system after I took a look under the air-intake throttle. Once I got the intake manifold off, I was pretty sure I figured out why the truck wouldn't start, even though it had spark, fuel, and air. The injector assembly along with the interior of the manifold was covered in black gunk. When I pulled the injectors out of their seats, the butterfly handles broke off they were so brittle. It appears that these have never been changed and I theorize that they were not seated properly due to the amount of goo that covered everything - as in fuel spraying back into the manifold. I've got the injector assembly on order and will post here once I get it installed. Hopefully, this will solve most of the problems.

The black "gunk" is perfectly normal. When the EGR valve opens, the entire plenum is filled with exhaust & air. If there are areas where it appears to be "washed", (golden color) that would indicate a fuel leak.

what is this know problem your talking about i am having the same problem on a 1997 that i just put a new engine in and No start fuel spark and right timing ive redone the timing on it so many times

This thread explains: https://blazerforum.com/forum/articl...-switch-33465/

So I'm going to heed the last responder's advice and check the ignition switch. I don't have the money to throw parts at it until it starts, though I wish I did. One thing that has me curious that it may be the ignition switch is that the headlights don't completely turn off unless the key is turned off. They stay on dim (less than low-beam brightness) even when the light switch is turned off. I understand this also may be the headlight switch itself, or even the relay, but if it is the ignition switch causing this, could it be possible that it's causing the vehicle not to start, too?

There are probably a dozen wires to the ignition switch. This means it supplies voltage to a dozen main circuits. DRL's, (Daytime Running Lights) is one of them, ignition is another, so yes, it can cause both to operate incorrectly.

So, here's something interesting. It appears that the mechanic who looked at this before I bought it drained the coolant from it. Would no coolant in it cause a no-start situation? Additionally, it appears that the thermostat is stuck wide-open. He did say the thing overheated when it stopped running.

Without coolant, the engine should still start & run. If the engine is running without coolant, it will overheat. If it gets too hot, it might stall and not start until it cools down. If there's coolant is in the engine, and the thermostat sticks open, it will not overheat. There's something going on that doesn't make sense yet, there's another piece of the puzzle somewhere. Did you check the circuits at the ignition switch? Did you check fuel pressure and leakdown?

Tested the fuel pressure this morning. Jumps to 60 psi when ignition switched on ( not started). It immediately goes down to 50 and then bleeds down to about 45psi. This tells me that both the injectors are leaking and that the fuel pump needs replacing. Additional thoughts, anyone?

60psi is borderline low and the leakdown is excessive. The results of the test are telling you that there are 2 problems, it does not tell you what they are, or where they are. Next step is to check fuel pressure and leakdown at the fuel filter. All fuel flow and pressure must dead end at the fuel pressure tester. When the pump is running, pressure must be 73psi to 108psi and must remain above 55 psi for at least 10 minutes after the pump shuts off. Results of this test will tell if the problems are in the tank or in the plenum.

Okay. So I tested the pressure at the filter by the tank and I have 65 psi which jumped down to 50 and then bled to 40, at which point I determined that the pump is indeed bad. Next step is to replace the pump. I'm guessing this won't help with the pressure bleed down, and that I'll also need to replace the injector assembly, too. The guy at O' Reilly's said I should get the "replacement" injector assembly for $300 to save myself from having to re-install the OEM injectors down the road. This new assembly has fatter tubes and the ends, or poppets, each have 2 wires going to them. What has anyone heard about these? Would I be wasting money or gaining reliability by purchasing this?

65psi at the filter.... Did all fuel flow and pressure dead end at the fuel pressure tester? In other words, no fuel is allowed past the filter.

With a reading of 65psi, I'm guessing you didn't have it dead end. 65psi is very close to regulated fuel pressure.... that's not what we're looking for with this test.

If it dead ended at the tester, the pump maximum output pressure is far too low AND the leakdown is excessive. In which case, the pump may be the only problem.

EDIT: The injector upgrade eliminates the poppets and relocates the injectors to the intake ports. It's a great upgrade IF you have problems with the existing injectors or regulator.

Yes. Dead ended - used a cap nut on the tester fitting. I see what you mean about the bleed down. I tested with a new fuel filter so it was flowing through as well as with a cap nut. With cap nut, I was only able to get about 65 psi that held steady, without - massive bleed down. I'll replace the pump and post back.

Anyone ever heard of collapsed rings or a broken cam shaft due to overheating? I'm going to check compression on all cylinders (except no. 3, which is behind the steering rod). I was talking to a mechanic who was in the parts store tonight. He said the 4.3 liters along with some other motors like Subarus, don't hold up well when overheated. The above-mentioned symptoms are the result when over heated. There's also the possibility that if the camshaft breaks, compression will show normal on a few of the cylinders, but nothing on others (front of motor vs. back).

Been working on these things since they started making them back in the late 80's, never heard of overheating causing issues like that. Easy way to get at #3 cyl is disconnect the steering shaft at the gear box and move it out of the way... 5 minutes. If the cam breaks, yes, compression would show up as you said. You could remove a rocker arm cover, crank the starter, and watch the rocker arms and confirm that very easily.

I would change plugs wires and rotor and cap maybe the cap is worn or cracked. Or the idiot may have put it on 180 off could very well be trying to start with 4 instead of 1 wont start make sure your wires are good and going to the right plug driver side 1,3,5. Pass side is 2,4,6 from front of motor to back most important is the rotor and cap if theyre not in correct firing order youll never get it started one the rotor should be at 8 oclock possition or seven depending on your cap the worst case scenario could be someone took your distributor out and put it in a tooth off or 180 off. Id check rotors possition tdc the engine take cap off and look at possition of the rotor if it lines up with the tab on cap and the cap is labelled 1-6 on top but be careful follow the number to the contact inside cap if thier in same place it should run if not then your distributors not in right. So first make sure rotar and cap are right then make sure wires are right connected. If not distributor pickup coil problem either someone put distributor in a tooth off or pickup coil bad

negative get spark plug socket slide on 3 plug then get a box wrench on the back side of the socket comes out like butter no needv for insanity

the cmpression should be no more than 10 percent difference in any cylinder higher or lower anything more or less rebuikd

check 3 by putting a spark plug socket on by hand then get box wrench on back side of socket comes out easy, put back in by hand with socket tighten back up with box wrench easy and i highly doubt you broke your cam from overheating doing this for 25 yrs never seen that happen. Blown head gaskets happen first and youd know this right away as all compression would be low. If your compression in all cylinders is less than 10 percent difference then motor is good. Youy antifreeze is not mixed with your oil then 90 percent sure didnt blow head gasket. Sounds like the mechanic that hyad this truck didnt know his ass from his job. I think it will come down to distributor or wires not right in correct order on motor or distributor cap or the distributor was moved a tooth or so off. Had this problem i changed distibutor and made sure wires were correct on motor and on cap as well as rotor and cap beeing put on right possition

he drained it for a reason so that it didnt mix with the oil he new it had a blown head gasket or assumed it did cause the first thing i check is oil is it clean is antifreeze mixed in it. The most common failure to any vehicle all when overheating is head gasket they crack they also crack heads and blocks did you fill it probably the problem is its got to run and have pressure in the engine for you to truely know if antifreeze is leaking into oil or pouring out the head or block that could be cracked the only reason for this so called mechanic to empty it would be to mislead someone by not knowing the extent of the overheating. And so you wouldnt notice mixed oil and antifreeze or leaks from cracked heads or engine block. The main concern would be geting a compression test on all 6 cylinders at least the 5 you can get to easily and if that checks out then im saying its something to do with cap rotor or distributor. Driver side 1,3,5 pass side 2,4,6 front to back cap is numbered also follow one on cap on side mount caps be careful following tabfrom cap top to inside tab if the rotor is at 7-8 oclock possition and the tab inside cap lines up thats good if not your off 180 degrees if its pointing at 6 rotor is on backwards. Make sure to tdc the engine before checking DISTRIBUTOR tdc timimg marks on harmonic balancer will point to 0 on gauge in front lower motor behind the harmonic balancer. IF YOU WANT 3 OUT ITS SIMPLE TAKE A SPARK PLUG SOCKET AND PUT IOT ON 3 BY HAND THEN GET A BOX WRENCH ON THE END OF THE SOCKET THE BOX WRENCH IS TURNING SIDEWAYS WHICH PARRALEL WITH COLUNM ELIMINATES TAKING STERRING COLUNM **** AND GEARBOX OFF I GAURANTEE THIS IVE DONE IT MANY TIMES WHEN YOU PUT IT BACK STUFF PLUG IN SOCKET START BY HAND THEN USE BOX WRENCH TO FINISH TIGHTENNING IT THERE ALWAYS A TRICK TO SAVE YOUR SANITY.

Back at it
 

Well, I let it sit for a while and am back at it. I pulled off the distributor cap and everything looks correct. Tab is between 7 and 8 O'Clock. While Turner ng the engine with a wrench, I felt NO COMPRESSION. I tested all holes and they're all dead. So, unless I find a new motor on CL locally for cheap, I'll be rebuilding it. Anything I should know before going into it? I've rebuilt motors before but am looking to do the least amount possible here. Maybe go in from the bottom on an engine stand and replace the rings. Is this wise? Any recommendations or thoughts are appreciated. Thanks in advance!

The reason for the headlights being dim is that the lighting system has DRL (Daytime Running Lights). It will turn the headlights on at reduced voltage. To bypass this while servicing the truck, you have to put the parking brake on. To bypass the DRL feature all together, just pull out the fuse for the DRL.

Or just get a swivel spark plug socket.

You do realize this thread is over 6 years old...….. time to retire it.